1. Field of the Invention
The present invention relates to an image signal recording and reproducing apparatus, and more particularly to an apparatus for recording and reproducing a plurality of lines of an image at the same time by use of a vertical scan mechanism of a head array having a plurality of magnetic head gaps and a signal processing apparatus thereof.
2. Description of the Prior Art
Generally, a magnetic recording and reproducing mechanism of a Video Cassette Recorder(VCR) or an Audio Tape Recorder is constituted in order to slide a recording medium, for example, a magnetic tape or a magnetic disk, on gaps of a magnetic head. In comparison with an audio head, a video head is installed around a rotating drum since a relative speed between recording media and the magnetic head should be high in the VCR. Therefore, a construction of the rotating drum is complicated and the size thereof becomes bigger.
In this case, a recording format is made such that image signals are usually recorded in largest portion of the tape in the widthwise direction and audio and control signals are recorded at edge portions of the tape in the longitudinal direction. A helical scanning method performs scanning of of a tape by a drum of a VCR which is rotated at an angle respect to a moving direction of the tape while contacting the tape with the rotating drum. In such a case, the long tracks are formed slantwise on the width of the tape, and a plurality of signals, for example, the one field image signals, are recorded and reproduced sequentially on and from each of the tracks.
In a VCR system employing the typical helical-scan method, in order not to vary the time axis of an image signal during recording and reproducing mechanism, it is necessary to control the rotation of the drum stably. And in case of the reproducing mechanism, for obtaining an optimal value of a signal-to-noise ratio through an accurate tracking control, it is necessary to use a drum servo circuit for controlling a rotation of a drum and a capstan servo circuit for the accurate tracking control.
Magneto-Resistive heads(MR head) utilizing a magneto-resistive film have been used more and more widely.
The reproduction output of the above-mentioned MR heads does not depend on a relative speed between recording media and a magnetic head, and in particular a sensitivity higher than that of a conventional inductive head is obtained at a lower relative speed. In such a case, a constant magnetic field which is called a bias magnetic field is applied to the MR head from the exterior in order to improve a sensitivity and a linearity of a magneto-resistive head. A number of methods for realizing the bias magnetic field have been proposed as follows:
(1) a method by which a permanent magnet is arranged in the proximity of an MR film;
(2) a method by which a conductive film is placed in contact with an MR film; and
(3) a method by which a soft magnetic film is arranged in the proximity of an MR film.
According to the development of these MR heads using a thin film technology, it could be possible to obviate the need for a head-to-tape high relative speed by use of a stationary multitrack magnetic head, whereby each of "line signals", which is called "line" hereinafter, of an image is simultaneously recorded in parallel on a relatively slow moving tape.
The technologies that are relevant to the MR head and multitrack magnetic head are disclosed in the following U.S. Pat. No. 4,816,948, issued Mar. 28, 1989, to Yoshihisa and U.S. Pat. No. 4,158,213 issued Jun. 12, 1979, to Grifis.